A direct broadcast satellite system has been proposed which will transmit compressed television and other ancillary signals in compressed and packeted form. The system has a potential of transmitting hundreds of programs. Each program may include a number of services. A service is defined herein as a program component, such as a video signal, or an audio signal, or a closed caption signal, or data, etc. The data may include executable computer files or programs for use by appropriate receivers. Each service of each program is identified by a unique service identifier (SCID). Thus if a program includes four service components, the program will be assigned four SCIDs. The information for respective services will be transmitted in packets of predetermined amounts of data (for example 130 bytes) and each packet of information will include a SCID corresponding to the service.
A plurality of programs, for example six to eight, may be transmitted in time division multiplexed form (on a packet basis) on a single carrier frequency. To provide, e.g. 160 programs, the system will transmit on 20 to 28 carriers.
In order to receive a particular program, a receiver is tuned to a particular carrier, and programmed to select signal packets associated with the program. Information associating the service components (SCIDs) with a particular program are contained in a program guide, which is itself a program that is transmitted. Because of the large number of programs and the consequential larger number of services, the programming information associating programs with services is ever changing, and must be continually updated.
The program guide includes information to be used by respective receivers to associate transmitted time division multiplexed service packets with programs desired to be viewed. The program guide is a program which is assigned a particular SCID that a receiver will automatically select on start up, and load the program data in memory. The receiver will include a microprocessor, which is responsive to programming commands, to scan the stored program guide and determine the carrier on which a desired program is transmitted and the associated SCIDs of the program's service components. Thereafter the tuner within the receiver will be tuned to the appropriate carrier frequency and packet selection apparatus will route the selected service component packets to corresponding signal processing apparatus.
The program guide information that has been discussed thus far is only machine usable, that is, the SCID information is useful to receiver apparatus but not of interest to the user. Information of interest to the respective user is the schedule of programs, the times of broadcast, the cost of pay per view programs, what movies or sporting events will be shown, etc. All of this data may also be included in the program guide and arranged in a form conducive to display and perusal. The display and perusal may be performed by conventional menu programming using the receiver On Screen Display apparatus.
The amount of program guide information for a month, for example, is enormous and places constraints on how, when and where it is transmitted and how, when and by what it is processed in respective receivers. One transmission parameter of paramount importance, which is impacted by the program guide is signal bandwidth. One receiver parameter of paramount importance is cost. The requisite use of program guide information should not significantly impact on either system bandwidth or receiver cost. In addition, the program guide should be available to the user with minimal delay.